Planning safe routes down the mountain

In Vale S/A’s CAD drawing, the green path represents a safe turning radius corresponding to the design speed for mining trucks leaving the Itabiritos Peak Complex. Drivers and vehicles that don’t follow the path at the design speed risk rolling over, leading to safety concerns, extra costs, and delays.

When mining trucks and steep, winding roads meet, more emphasis must be placed on safety. Around the world, mining companies face enormous time and financial pressures to get the natural resources out of the ground. If a truck tips over on the way from the mining site to the processing plant, the consequences can be serious. With today’s road design software technology, that kind of mistake is preventable.

Vale S/A, one of the biggest mining companies in the world, operates several mines in Minas Gerais in the eastern part of Brazil. In Minas Gerais, the fourth largest state in the country, the mountains and valleys are rich with iron ore deposits, which fuel the steel mills farther to the south of the capital of Belo Horizonte. With dozens of mines in the area, big mining trucks are a common sight on the roads. Roads are built based on the kinds of trucks needed for the mining operations and keeping them safe is an important job for the trucking companies.

One of the country’s oldest ore deposits is located at the Itabiritos Peak Complex, consisting of the Chicken Coop, Pico, and Sapecado iron ore mines. According to Antônio Carlos De Miranda Francisco, one of Vale S/A’s production engineers who help design roads for the mines, there are many years of production remaining at the site.

“The operation began in the early years of the 1940s, so they have already had 74 years of operation of the project,” Francisco said. “The expectation is that the mines in Sapecado and Galinheiro will be exhausted in 2035 and 2039, respectively.”

Figure 1: Relationship between vehicle speed and turning radius.

Francisco began using AutoTURN software in 2013 to perform investigative analysis when a Mercedes Benz 6x4 truck tipped over while leaving the Itabiritos Pico mine area. The accident occurred at night, when the truck operator entered a roundabout too fast, where the maximum recommended speed is 17 km/h. In addition to the roundabout investigation, he has used AutoTURN to plan road geometry around the Itabiritos Peak Complex.

Mining companies in Brazil must follow guidelines from the Ministry of Labor and Employment, including NR-022. This guideline states that the minimum width of lanes in open cast mines should be twice the width of the largest vehicle used in single lane roads and three times greater than the width of the largest vehicle used on a four-lane highway.

“The AutoTURN software played a key role in the analysis of road geometries in the mines, mainly in the width parameter of the curves, where we know there is a need to have a larger size than in the straight sections,” Francisco said. “Although we have to follow the NR-022 regulations of the labor ministry, it usually occurs in situations where the roads need to adjust to the various models of vehicles traveling to the mine. AutoTURN helps us streamline operations in determining bottlenecks in the flow of transport vehicles and also helps us improve the safety aspect.”

After the accident, Francisco used AutoTURN’s vehicle swept path capabilities to evaluate the speed at which the truck was travelling and the turn radius the driver was using. The Vale S/A safety committee wanted to learn what speeds were acceptable within the safety ranges. He gathered data from the trucking company and from local authorities to make his calculations for the AutoTURN simulation.

“It was a question regarding the speed of the operator at the time of the accident,” Francisco said. “The safety committee approached us to help them identify the radius of the trajectory performed by the truck in order to then calculate the average speed.”

Engineers at Transoft Solutions have applied extensive research to the relationship between vehicle speed and turning radius (see Figure 1). AutoTURN software demonstrates that the higher the speed of the vehicle entering the turn, the larger the turning radius. Francisco used the vehicle libraries within AutoTURN to find key measurements for the Mercedes Benz 6x4 truck and recreated the road geometry where the accident took place. With AutoTURN providing insights on the optimal path and speed of the vehicle, he could show what needed to change.

“The starting point of the work was to identify the correct position of the truck at the instant that the accident took place,” Francisco said. “This was achieved by simulating the overturning truck, placing it in the normal position, with all wheels on the ground, and calculating the offset distance from the curb of the median island of the roundabout. This measure was taken by the safety team when the truck was still overturned. The actual distance was determined by subtracting the width of the vehicle.”

Truck drivers going to and from the Itabiritos Peak Complex sometimes contend with a lack of visibility on some of the turns and lane widths, which are too narrow on some sections of road. Francisco studied the accident data carefully and showed the Vale S/A safety committee what speeds were recommended for safe transport of the iron ore to the processing facility.

“Our technical team can evaluate the truck routes to our iron ore mining sites with greater accuracy and confidence,” Francisco said. “We now know critical points along the route that must be changed to make things like the turning radii and working width safer.”

Before starting his career with Vale S/A, Francisco used AutoTURN as a graduate student at Faculdade Pitagoras. He knew firsthand that the software could help him with his work with Vale S/A. “We learned about AutoTURN through a term paper that I wrote with some other students as part of my program to graduate with a production engineering degree,” he said. “After combining AutoTURN with InVision, we could analyze the safety considerations of our transport fleet of small, medium, and large off-road trucks.”